Alhagi maurorum extract modulates quorum sensing genes and biofilm formation in Proteus mirabilis

Proteus mirabilis (P. mirabilis) is a frequent cause of catheter-associated urinary tract infections. This study aims to investigate the anti-infective effect of Alhagi maurorum extract (AME), the traditional medicinal plant in the middle east, on the biofilm-forming P. mirabilis isolates. Hydroalcoholic extract and oil of A. maurorum were characterized by HPLC and GC–MS. The antiproliferative, anti-biofilm, and bactericidal activity of AME at various concentrations were assessed by turbidity, crystal violet binding, and agar well diffusion assays, respectively. The AME’s effect on adhesion and quorum sensing (QS) were investigated by in vitro adhesion assay on cell culture and agar overlay assay using Janthinobacterium lividum (ATCC 12472) as a biosensor strain. In addition, the expression level of selected genes involved in QS and biofilm regulation were determined by quantitative Real-Time PCR. Furthermore, the bladder phantom model was created to evaluate the assays and investigate the catheter’s calcium deposition. The most effective chemical compounds found in AME were tamarixetin, quercetin, and trans-anethole. Although AME did not inhibit swarming motility, it reduced biofilm production and exerted a concentration-dependent anti-adhesive and anti-QS activity against P. mirabilis. AME also downregulated the expression level of selected genes involved in biofilm formation and QS. This study showed that AME as a natural compound reduced biofilm formation of P. mirabilis by targeting virulence factor genes, quorum sensing, and other strategies that include preventing the adhesion of P. mirabilis to the cells. The results suggest that A. maurorum extract might have the potential to be considered for preventing UTIs caused by P. mirabilis.